The advent of HIV protease inhibitor (PI) therapy was a major advance in the treatment of HIV infection. Combined treatment of HIV-infected patients with reverse transcriptase inhibitors and PIs (Highly Active Antiretroviral Therapy, HAART) has been shown to delay the onset of overt disease and to prolong survival. Current guidelines recommend the use of HAART for the treatment of all newly diagnosed cases of HIV infection. Unfortunately, HAART is associated with the development of numerous metabolic abnormalities, including peripheral lipodystrophy, hyperlipemia, insulin resistance, glucose intolerance, and type 2 diabetes. The reported incidence of type 2 diabetes in PI -treated patients is at least ten-fold greater than that in the general age- and sex-matched population and is particularly alarming considering the relatively young age of the patient populations and the rapidity of diabetes onset after the start of therapy. PIs have been shown to rapidly and selectively suppress the activity of Glut4, the insulin-responsive glucose transporter, an effect that contributes to the insulin resistance and increased incidence of diabetes associated with PI therapy. Additionally, PI-mediated inhibition of glucose transport into pancreatic beta cells appears to reduce glucose-stimulated insulin secretion, which most likely also contributes to the development of overt diabetes. These observations support a global hypothesis whereby the direct binding of PIs to glucose transporters leads to a constellation of biochemical perturbations that ultimately results in the PI-associated metabolic syndrome. The long-term goal of this proposal is to further explore this hypothesis and to determine the mechanism of the effect of PIs on glucose transport activity. [unreadable] To accomplish these goals, the following specific aims will be pursued: [unreadable] 1) To test the hypothesis that PIs suppress insulin-stimulated glucose transport by direct binding to Glut4. If this hypothesis is validated by crosslinking studies, the structural determinants of Glut4 interaction with PIs will be mapped by analysis of chimeric and mutant glucose transporters. [unreadable] 2) To test the hypothesis that PI-mediated inhibition of glucose transport directly contributes to lipodystrophy by suppressing adipogenesis and/or by enhancing adipocyte apoptosis. [unreadable] [unreadable] [unreadable]